Recording sound photographically



March 14, 1.939.

.1. EGGERT Er A1.

RECORDING lSOUND PHOTOGRAPHICALLY Filed Jan- 26,l 1934 f//m )5r/flereversa/process Y lnven fors:

Patented Mar. 14, 1939 Y UNITED STATES ling-ENT4 OFFCE RECORDING SOUNDPHOT()GrRAIHICALLY- John Eggert, Leipzig-Gohlis, and Alfred Kster,

Dessau in Anhalt, Germany, assignors to I. G. -Farbenindustrie-Aktiengesellszhafh Frankforton-the-Main, Germany Application January26, 1934, Serial No. i708,506 In Germany January 28, 1933 6 Claims.`(Ci. 274-46) Our present invention relates to photographic fy=1,-1.5. Inthis oase an increase of-density of sound recording; about 1.4 to 1.6may be selected. This may be One of its objects is to provide a processof achieved, for instance, by recording sound on producing aphotographic sound record according photographic layers having so low .acontent of 5 to the reversal method. Further objects will be silver, oron'layers being so thin that the-silver 5 seen from the detailedspecication following halide contained in them suffices only -to producehereafter.

adensity of 1.8 after the first development if the In developingphotographic sound records aclm is exposed throughout the thicknessofthe cording to the reversal method a sound track photographic layer.Or, when using a layer with m is obtained which yields a bad renderingof frea normal content of silver, precautions can be l0 quencies. Thecause resides in the fact that, for taken that only part of. 'theunchanged silver instance, for the recording of sounds according tobromide which is left afterlthe first development the variable areamethod, an extremely strong is utilized for theA production of" the nalsound first exposure must be applied in order to obtain record. Measuressuitable to this effect are,for

v1 5 the minimum density that is to say the density instance, a dosedsecond exposure or a dosed 16 which, corresponds with the fog of thephosecond development, or a reduction of the residual tographicmaterial.v This is clear when considerpicture of silver bromide priorvto the second dey ing that of a sectionv of nlm which after reversalvelopment, or the like. shall have only the density caused' by the un- Apreliminary exposure'of the film 'to the reavoidable fog, the emulsionlayer must be blackquired light intensity and limited to the zone of' 20ened throughout its thickness by the first exthe lm which is toreceivegthe sound record, is posure and the first development so thatthe also asuitable-expedient. silver is completely removedfrom thissection in The eiect of a dosed second -exposure on the the bleachingoperation. In thereversal processes reversal development of acinematographic lm usual in the making of cinematographic pictures, isillustrated, by Way of example, in the accom- 25 the lowest possibledensity, after reversal, is obpanying drawing, in which the exposurecurves tained Only With densities 0f between 2.5 and 3, of a negativeand of `positives obtained accordmeasured after the rst development.Considering to' a normal reversal process and according ins theextraordinarily large amOuntS 0f light t0 `to a process using a dosedsecond exposure are which the layer, for obtaining so intense a density.shown. i i Y 30 must be exposed, it is evident that the reproduc- In thedrawing the negative curve" represents tion of high frequencies isheavily impaired owing the density produced in the ilrst development ofto'spreading, the reversal vfilm as a function of the exposure,

According to the present invention' the course whereas the normalreversal curve represents 0I frequencies 0I a Sound record on'reversallm the densitiesobtained after dissolution of the nrst as iS,Consider-ably imPrOVed by Conducting the exsilver pictureand after thesecond development posure during 'the recording of sound and the fur-`of the silver bromide residual-picture which hasf y ther manipulationoi the lm in sucha manner been exposed throughout. Ifthis normalreversal that the density ebtined after the rSt develepis'to yield,during the second development, a nor- 40 ment, that iS t0 Se? thehighest density 0f the mal minimum density of about 0.17,'-that is to 40negative, which corresponds with the lowest DOs# say the density due tothe fog of the illm, there, sible density after reversal, that is to saywith must be obtained as appears from the curves, a the density causedbythe fog, does not exceed very'intense density during the firstexposure,-

8 Veille 0f `Stimuli 1-8 density units. The density which according tothe present example would be D iS Calculated from the `formula: realizedby an exposure of log I.t=3.13,V in which 45 y incident u ht formula Iis the intensity and t the time .of exn mitad. ht posure.- When applyingso intense a first exl a g posure therewould be produced a heavy spread-This value is obviously dependent upon the lus. so that the reversedsound illm 4would'be gradatlon of the emulsion to a. certain extent sopractically useless# 50 that only emulsions having a fy 1 should beused. However', by A(1081118 the emelmt 0f light em- In the case of y 1the exposure must producean ployed in the second exposure, for instanceby increase o! density-less than 1.,8. It may also be 'reducing thesour-'ceci light, which ata' voltage preferable to use an increase o!density less than of 220 operates a complete illumination. to a 1.8 intle neighbourhood oi "vgl, 'for instance voltage ci 1 20. the reversalcurve with dond ex- 55 isobtained. maximum density' oi only 1.45 on thenegative curve corre- V'still-liesontherectilirie/arpartoithetrlmsspendswith a minimum density oil only 0.07 onthe reversal curve. To thisendthe exposure is enected in recording vsound with, an intensity otlight oi' log I.t'=1.8 only, so that spreading inthe sound record neednot be feared.

I! the aforesaid mode of operation is appliedfor the registration o!sounds according to the variable density method the highest density isgiven only such a value'(in any case below d=l.8), that after the dosedexposure and reversal the minimum density lies so much above vthedensity due to the tog '(for instance d=0.25)

that the corresponding value oi the transparency parency curve. l

The process of recording sounds on reversal nlm as described may be usedfor the production oi' nlms bearing besides the sound record also a Vpicture record.

'y records ons moving reversal nlm having a q 'l Y Whatweclaimis: lLAprocessotproducing photographic sound records on a' moving reversalillxnA having a l1y 1 and provided with a' silver emulsion whichcomprises modulating a; beam -of light in accordance withA soundvibrations, projecting said beam o!lightonsaidreversalnlm,themamumexposure' producing a density on the nlmoi.' not more than about 1.8, working up the nlm in sucha manner thataiter it hasbeen treated according to. the reversal method, the minimumdensity on the lnlm corresponding with the maximum y lexposure issubstantially equal to the`density ci! the I og.

posure producing a density on'the nlmoinot .more than about 1.8,.saidreversal nlm having `beenpreexposetltosuchanextentthatthemaximum'expcs'urein recording sound produces adensityotthenlmthataiterreversaltheplaces oi maximum exposure onthe nlmshowa minimumuensity substantially equal msm density' of the iogofvthennished nlm. and working up the-nlm accordingto the reversal method..

3.- a process of producing photographic'sounciI records ona'moving-reversal nlm having a 'y '1.andprovidedwithasilverhalideemilsionwhich comprises modulating abeanieslight in acsaid andere illm a second time.

beam oilight on said reversal nlm, regulating the intensity of saidprojected light so' that the maximum exposure produces a density on .thenlm of not more than about 1.8, developing said nlm, removing thesilver, exposing said nlm a second time to actinic light, regulating'the' amount o! said light so that after a further de,-

velopment the minimum density on the nlm corresponding lwith `themaximum exposure is substantially equal to the density of the fog of theand nxing said nlm.

4. A process of producing photographic soun records on a movingreversalnlm having a 7 1 andprovided with a silver halide emulsion,which comprises modulating a beam ci light in accordance with soundvibrations, projecting said beam of light on said reversal nlm, themaximum exposure producing a density on the nlm ci not more'than about1.8, developing said nlm, removing the silver. exposingsaid nlm a secondtime to actinic light, developing said nlm a secori'd time to such anextent that after a further nxingoperation the minimum density onthe nlmcorresponding with the maximum exposure-is substantially equal to thedensityof the fog ot the4 nnished nlm, and nxing Vsaid nlm.

5.l A process oiproducing photographic sound records on a movingreversal nlm having a 7 1 and provided wltha silver halide emulsionwhich comprises modulating a beam oi' light in accordance with soundvibrations, projectingx said beam of light on said-reversal nlm, saidreversal nlm containing so much silver that the exposure pre-r, ducesamaximum density of 1.8, and working up the' nim vaccording to thereversal method. l'

' 6. A process ci producing photographicv sound l records on a movingreversal nlm having a Q1l and providedwith a silver halide emulsion,which comprises modulatingy a beam oi light in accord-l ance with soundvibrations, projecting said beam of light on .said reversal nlm, themaximum exposure producing aldensity' on. the nlm of not more than about1.8, developing said nlm, removing the silver, exposing said nlm asecond time toactinic light, reducing theremaining amount of the silverhalide in` a nxingbath until after al second development the minimumdensity on .f

the/nlm corresponding with the maximum vexposure is substantially equalto the density of the io'g o! the yiinished nlm, -anddeveloping saidl YJOHN-sooner. 't

l i ,ALFRED xs'rsa.

10 nnishednlm, developing said nlm a second time, y

